Numerous forms of drive mechanisms for human-powered vehicles are known. Perhaps the most widely used is that found in a conventional bicycle wherein the rider provides power for the vehicle by producing rotary motion with his feet on a pedal/crank arrangement. The rotary force so produced is transferred to a driving wheel of the vehicle by means of a bicycle chain. Various forms of gear selection mechanisms may be interposed between the crank and the driving wheel and the vehicle itself may be provided with one or more wheels attached to a frame.
Drive mechanisms utilizing ratcheting gears to produce or transmit alternate driving forces to a driving wheel are also known and have been disclosed in references, such as U.S. Pat. No. 98,092, U.S. Pat. No. 1,154,208, U.S. Pat. No. 2,114,648, and U.S. Pat. No. 4,077,648.